The present invention relates to a superconducting rotating apparatus such as a superconducting generator in which at least a winding mounted on a rotor are composed of a superconductor. 2. Description of the Related Art
In a conventional generator, a field winding composed of a superconductor is contained in a rotor, and both end portions of a shaft of the rotor are rotatably supported by bearings. A stator has an armature winding spaced at a predetermined interval from the rotor, and mounted in a stator frame. The stator frame is connected to the bearings and supported to a base. A coupling for connecting a driving device to one shaft end portion of the rotor is provided on one side of the rotor, and a field current source for supplying a field current to a field winding and a coolant supply source for supplying coolant into the rotor are provided on the other shaft end portion of the rotor.
The rotor of the superconducting generator has complicated mechanism and parts for holding the superconductors at a superconducting temperature. For example, a cold rotor for containing the field winding is heat-shielded from the exterior to hold the superconductors at a superconducting temperature, and constructed in a structure to be cooled with coolant. More specifically, a heat shielding cylinder having a mirror-surface state on the surface and a magnetic shielding cylinder for shielding the field winding against a detrimental magnetism from the armature are arranged concentrically on the outer periphery of the cold rotor, and rooms formed among the cold rotor, the heat shielding cylinder and the magnetic shielding cylinder are respectively formed in vacuum rooms held in vacuum. Therefore, conduction of heat to be introduced from the outer periphery into the cold rotor is prevented by the vacuum rooms, and radiant heat is radiation-shielded by the mirror-surface of the heat shielding cylinder. A torque tube of a thin hollow cylindrical structure and a radiation shield formed on the surface in a mirror-surface state for blocking the opening end of the torque tube are provided at the shaft ends of the cold rotor, and a room formed between the shaft end portion side of the rotor and the radiation shield and rooms formed in the torque tube are formed in vacuum rooms held in vacuum. Therefore, heat transfer of the heat to be introduced axially to the rotor is prevented by the vacuum rooms, and radiant heat is shielded by the mirror-surface of the radiation shield. Further, structural members around the cold rotor can be forcibly cooled by coolant, thereby strengthening to cool the cold rotor.
On the other hand, coolant supplied into and discharged out of the rotor is guided from a central hole formed at the shaft end portion of the rotor at the opposite side to the coupling into the rotor through a supply tube. In this case, since a radially outward force is applied to the coolant by a rotating centrifugal force, the coolant introduced into the cold rotor passes through a passage in the cold rotor to cool the field winding. Since the coolant raised at the temperature is reduced in the specific weight, the coolant supplied from the supply tube is gathered at the radially outside in the low temperature room in the rotor and the coolant which has cooled the room and been raised at the temperature is gathered at the central portion. Part of the coolant raised at the temperature evaporates at the control portion. The evaporated coolant gathered at the central portion can be discharged from the drain hole through a drain tube.
In the above-described superconducting generator, an exhaust tube for evacuating the vacuum rooms around the supply tube and the drain tube in the cold rotor in vacuum state is provided to heat shield among the supply coolant and the drain coolant and the rotor. In this conventional example, the vacuum rooms communicate with a vacuum pumping hole provided at the shaft end portion at the opposite side to the coupling in order to vacuum from a corresponding fixed section.
With respect to the rotor shaft end portion of the coolant supply/drain structure and the corresponding fixed section, a coolant supply device of the fixed section is partitioned therein by a plurality of flange members arranged axially at a plurality of positions spaced from the outer periphery of the rotor, and a sealing mechanism is provided in a gap between the flange members and a rotor shaft. Thus, the central hole, the drain hole and the vacuum pumping hole of the rotor shaft can communicate independently with the opposed rooms in the coolant supply device as the fixed sections. In the coolant supply device, a transfer tube communicating with a coolant supply/recovery device and a vacuum pumping tube communicating with a vacuum pumping device can be mounted in the coolant supply device, and can communicate independently with the central hole, the drain hole and the vacuum pumping hole of the rotor.
A magnet and a pair of pole pieces made of a magnetic material are disposed on the inner periphery of the flange portion, and magnetic sections having flange-shaped stages are disposed on the outer periphery of the opposed rotor shaft end portion. Magnetic fluid is poured between the stage and the pole pieces disposed as described above to be completely filled between the stage and the pole pieces to form a sealed wall without disturbing the rotation of the rotor and without contaminating the peripheral atmosphere.
However, in the above-described superconducting generator, there are problems as will be described below.
(1) Since the cold rotor is mechanically connected with the structual members of the outer rotor, external heat is conductively introduced to the cold rotor. PA1 (2) External heat is conductively introduced to the cold rotor through current leads for supplying the field current to the field winding. PA1 (3) Since the portion of the current leads is generally made of a normal conducting conductor, the cold rotor is heated by Joule heat generated by the field current. PA1 (4) It is necessary to always supply coolant during operation to suppress the temperature rise of the cold rotor and to hold the superconductor which composes the field winding at the superconducting temperature, and the necessary capacity of the coolant supply device must be large. PA1 (5) Coolant flowing loss is generated when the coolant is supplied to the low temperature room of the cold rotor through the supply tube, and the supply tube itself is a heat transfer passage to introduce external head to the rotor. PA1 (6) Since one shaft end portion of the rotor is occupied to supply the coolant as described above, it is difficult to mount other structural parts on this shaft end portion. Since it becomes difficult to hold sealing performance as the above-described sealing mechanism is larger in diameter and thus, higher at circumferential speed, it is difficult to connect directly a shaft for operating a high torque.